[Halld-tracking-hw] [CDC] preAmp follow up on todays meeting

[Yves Van Haarlem]

Hi Beni,

I was assuming they were noise, so I put the tracked versions of those 
plots below it. Those lines become much less pronounced but some of them 
are still there.

Cheers,
 	Yves


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On Fri, 9 Jul 2010, Beni Zihlmann wrote:

> Hi Yves,
> I have one question about the 2-dim histograms in
>
> http://www.jlab.org/Hall-D/software/wiki/index.php/Energy/Amplitude_as_a_function_of_drift_time
>
> the vertical bands clearly visible at channel 2000 and beyond are 
> equidistant. on the right plot
> one even sees hints for this bands below 2000. Do you know what that is?
>
> cheers,
> Beni 
>
>> Hi Lubomir,
>>
>> 
>>> - the maximum amplitude of the first peak (this is what you mean by 
>>> amplitude, right?)
>>> 
>> Yes
>>
>> 
>>> is almost constant, except at the extreme  track positions. One expects 
>>> this because this amplitude is related the cluster (or few clusters) that 
>>> is closest to the wire and should not depend on the path length. To make 
>>> sure that this correct, could you make a profile plot: the mean amplitude 
>>> vs drift time, excluding the overflow channels.
>>> 
>> I added this plot (non-tracked and tracked version) on
>> http://www.jlab.org/Hall-D/software/wiki/index.php/Energy/Amplitude_as_a_function_of_drift_time
>> 
>> It is fairly constant, there is a slow trend downwards.
>> 
>> Cheers,
>>  	Yves
>> 
>> 
>>
>> 
>>> Thanks,
>>> Lubomir
>>> 
>>> 
>>> 
>>> On Wed, 7 Jul 2010, Yves Van Haarlem wrote:
>>>
>>> 
>>>> Hi All,
>>>> 
>>>> This is to follow up on the discussion we had on todays meeting.
>>>> 
>>>> After watching Germany lose I locked myself up the lab and noticed that:
>>>> 
>>>> 1/ That weird noise peak, mentioned in the meeting, is caused by the 
>>>> thermo-couple. If I switch off the T-controller that peak disappears.  It 
>>>> makes sense because after we fixed a gas leak the thermocouple must have 
>>>> moved closer to the straws, it is around this time this noise appeared. 
>>>> -- problem solved at the moment by switching off the T monitoring. Also, 
>>>> the noise is higher in amplitude on straws close to the T-couple.
>>>> 
>>>> 2/ By comparing drift time spectra of the old preamp (as in the published 
>>>> paper) with the new preAMp at 2100V and 50-50 gas. It can be seen:
>>>> 
>>>> http://www.jlab.org/Hall-D/software/wiki/index.php/Drift_time_comparison_(gas_check)
>>>> 
>>>> that the new preAmp shows that the longest drift times are 100~ns shorter 
>>>> compared to the old measurement, this means that the gas mixtures are 
>>>> different. L'histoire se r?p?te: mysteries with the old pre-amp were 
>>>> explained by wrong settings of the gas flow controllers. Now the mystery 
>>>> of the new preAmp has again something to do with the gas mixture. Indeed 
>>>> Beni, it looks like a 60/40 Ar/CO2 gas: both drift-time as 
>>>> efficiency-curve wise. Back then the problem with the gas mixer was 
>>>> easily fixed because some settings were wrong, now it has to be something 
>>>> else.
>>>> 
>>>> Personally I do NOT think it is worth to send the preAmps back before we 
>>>> solve this gas problem. If you still want me to send them to J-lab please 
>>>> ask me to do so.
>>>> 
>>>> The way we can solve/avoid the gas problem is to compare with pre-mixed 
>>>> gas: we have 90-10 Ar-CO2 premixed. This will take time... Or we can 
>>>> order 50-50 premixed and repeat our studies, or we just put the 90-10 
>>>> premixed in and compare with the measurements done for the paper and 
>>>> track down problems with the gas mixer later. Personally I would go with 
>>>> the last options because this produces results concerning the new preAmp 
>>>> faster.
>>>> 
>>>> 
>>>> 3/ The plots requested by Lubomir with Energy/amplitude as a function of 
>>>> energy (using cosmics) can be found here:
>>>> 
>>>> http://www.jlab.org/Hall-D/software/wiki/index.php/Energy/Amplitude_as_a_function_of_drift_time
>>>> 
>>>> Expected behavior can be seen, this data is not tracked (to save time), 
>>>> so some noise hits are present. Let me know if you want the tracked 
>>>> version too.
>>>> 
>>>> Cheers,
>>>> 	Yves
>>>>